I have recently done a quick sketch rendering demo in my company, and I have prepared a step by step screenshots tutorial that I'd like to share here with you all.Basically it is showing what tools and techniques I use to render a quick concept sketch line drawing using the mouse only. No pen tablet is needed, really.The time I spent for this one is around 1 hour, including making the screenshots.

In my daily work, I think I must be able to render 8 of these illustrations in one day. They can be used for internal concepts reviews, or even reviewing with the client in the early concept stage.

Of course you can spend more time on more details, but for this demo the purpose is to quickly render the basic coloring,shading,lighting and highlights.

I have used the Eton Axis radio for this tutorial. This product is absolutely a great object to practice your sketching skills. It has basic geometries like cylinders and boxes. Actually I did a sketch demo for this one too, but I don't think I should cover that, as there are many good sketch demos available online already. By the way, my sketch is not perfect (ellipses are off), but it should be good enough

The following 4 Photoshop tools are the most important ones for this particular tutorial:

Check the layers window on the right. You'll see that layer 1 and 2 are actually the line drawings scans. I have put their layers in the 'multiply' mode to make the white background transparent.So below those I can put all the layers for the coloring. And I start with the main grey colors with selecting the related body surfaces with the polygonal lasso tool and use the paint bucket to fill it with a color

All right, we have just finished the basic coloring. Now put all the layers in a group, and copy this group (I have named the copy group 'step 2')
We are using these group of layers to do the shading and lighting. If you mess up, then you can use the original layers from the first group to redo.

Now we can start putting lighting and shading on the cylinder shapes, using the dodge and burn tools. Just adjust the size of the tool and sweep a couple of time over the surface that you want to edit.Starting with the shading first..